What is one action of the upper fibers of the trapezius?

The upper fibers of the trapezius muscle play a crucial role in shoulder movement. One of their primary actions is the elevation and upward rotation of the scapula. When the upper fibers contract, they help lift the scapula towards the ears, which is essential for various shoulder movements, such as raising the arms overhead. Additionally, the upward rotation is vital for the full range of motion of the arm during overhead activities, allowing the glenoid fossa of the scapula to face more upwards, facilitating movement at the shoulder joint. These coordinated actions are essential for proper functional movement, particularly in activities that require lifting or reaching.

In contrast, shoulder extension and solely scapular elevation do not encompass the full functional role of the trapezius's upper fibers, and medial rotation of the shoulder is not associated with this muscle's actions either. Understanding these distinct functions emphasizes the importance of the trapezius in maintaining proper shoulder mechanics and posture.